The color display circuit or the color encoder is a circuit for outputting video signals to output devices such as a color TTL monitor and the like by selecting the corresponding colors in accordance with the color information and/or the intensity information outputted from a computer and the like. Such a color display circuit is illustrated in FIG. 1, and is disclosed in Korean Utility Model Publication No. 85-1954.
The above circuit is constituted such that a color mode converting section 81 is automatically shifted to a 16-color/64-color mode by a color mode selector 82 in accordance with the positive or negative polarity of the vertical synchronizing signals inputted through input terminals C1-C8; and the color information corresponding to the 16-color/64-color mode inputted through the input terminals C1-C8 is supplied to a video signal combining section 83 in order to control the video signal outputt section 84, so that 16 colors or 64 colors are selectively displayed.
The video signal combining section 83 consists of D/A converters D/A1-D/A3 and combiners AD1-AD3, and the respective data of the color information are directly supplied to the combiners AD1-AD3 in the case of a 16-color mode, while, in the case of a 64-color mode, the respective data of the color information are supplied through the D/A converters D/A1-D/A3 to the combiners Ad1-AD3. Meanwhile, in the case of a 16-color mode, a bright color in formed by controlling a brightness adjusting section 85 by means of an intensity information, while, in the case of a 64-color mode, a contrast adjusting section 86 is controlled by the respective color data of the intensity information. Reference numeral 87 represents deflection and high voltage generating section.
However, in such a conventional color display circuit, the circuit system has a dual nature of the 16-color mode and the 64-color mode, and consequently, the constitution of the circuit is very complicated, with the result that the manufacturing cost for it becomes very high, thereby aggravating the economic feature. Further, in its form of the signals used in the circuit, digital and analogue signals are sometimes mixedly used depending on the mode, while the methods of controlling the video signal outputt section are different according to each mode, thereby making the designing of the circuit very troublesome. Further, in the case of a 16-color mode, the differences between the colors are not definite, and particularly, green and yellow colors are not discriminable, thus ultimately showing an insufficiency of color display.